Research On Electrolyte Optimization For Zinc Anode

The metal zinc anode has exceptionally high volumetric specific capacity(5855m Ah cm^-3)and low reduction potential（-0.762 V vs.SHE）,and the aqueous electrolyte is low-cost and non-flammable.Therefore,aqueous zinc-based batteries are considered to be one of the potential candidates for the large-scale energy storage system.The problems of dendrite growth,corrosion reaction and hydrogen evolution reaction have hindered the commercialization of metal zinc anode.To cope with the challenges faced by metal zinc anode,this paper,starting from electrolyte components regulation,respectively modified zinc sulfate electrolyte and zinc chloride electrolyte,effectively improves the zinc anode’s cycle performance.The main research contents are as follows:（1）L-cysteine was used to modify zinc sulfate electrolyte to inhibit the growth of zinc dendrite and improve the interfacial stability.Studies show that 0.2 g L^-1 cysteine can effectively inhibit zinc dendrites and improve the cycling stability of zinc anode.Compared with the ordinary zinc sulfate electrolyte,the electrochemical nucleation potential of zinc is reduced by 30 mV in the optimized electrolyte,and the corrosion current density is reduced from 1280μA cm^-2 to 6.04μA cm^-2.Due to the adsorption of cysteine on the surface of the zinc anode,the initial crystal nuclei of zinc are transformed from large and concentrated zinc clusters to uniformly dispersed and tiny zinc nuclei,which in turn induced uniform zinc deposition.Therefore,the zinc-zinc symmetric battery with the modified electrolyte can stably charge and discharge for more than 2800 hours at 1 mA cm^-2,1 mAh cm^-2.At the same time,it also has ultra-long cycle stability under the condition of large current density and large areal capacity.The zinc-iodine battery assembled with the iodine-loaded activated carbon cathode shows remarkable cycling stability over 3000 cycles,while the battery with the ordinary zinc sulfate electrolyte only cycled 138 cycles before short-circuiting.（2）For zinc chloride electrolyte,we studied the effect of different imidazolium chloride salts on crystal orientation and morphology of zinc deposits.In terms of crystal orientation,1-ethyl-3-methylimidazole chloride（EMIMC）and 1-butyl-2,3-dimethylimidazole chloride（BMMIMC）can promote the growth of zinc（002）crystal plane.In terms of the flatness of zinc deposition,EMIMC,BMIMC and BMMIMC are conducive to promoting the smoothness of zinc deposit,and the effect follows the following order:BMMIMC>BMIMC>EMIMC.The cycle life of symmetric cells with BMMIMC modified electrolyte can reach 2100 hours at 1 mA cm^-2,1 mAh cm^-2,which is 10 times as long as in zinc chloride electrolyte.The zinc-activated carbon capacitor exhibits stable cycling for more than 13000 cycles at 1 A g^-1.